In general, virtualization refers to the simultaneous hosting of one or more operating systems on a physical computer. Such virtual operating systems and their associated virtual resources are called virtual machines. Virtualization software sits between the virtual machines and the hardware of the physical computer. One example of virtualization software is ESX Server, by VMware, Inc. of Palo Alto, Calif. Other examples include Microsoft Virtual Server and Microsoft Windows Server Hyper-V, both by Microsoft Corporation of Redmond, Wash., and Sun xVM by Sun Microsystems Inc. of Santa Clara, Calif.
Virtualization software provides to each virtual operating system virtual resources, such as a virtual processor, virtual memory, a virtual network device, and a virtual disk. Each virtual machine has one or more virtual disks. Virtualization software typically stores the data of virtual disks in files on the filesystem of the physical computer, called virtual machine disk files (in the case of VMware virtual servers) or virtual hard disk image files (in the case of Microsoft virtual servers). For example, VMware's ESX Server provides the Virtual Machine File System (VMFS) for the storage of virtual machine disk files. A virtual machine reads data from and writes data to its virtual disk much the same way that an actual physical machine reads data from and writes data to an actual disk.
Traditionally, virtualization software vendors have enabled the backup of virtual machine data in one of two ways. A first method requires the installation of backup software on each virtual machine having data to be backed up and typically uses the same methods used to back up the data of physical computers to back up the virtual machine data. A second method backs up the files that store the virtual disks of the virtual machines, and may or may not require the installation of backup software on each virtual machine for which the data is to be backed up.
As an example of the second method, VMware Consolidated Backup (VCB), also by VMware, Inc., enables the backup of the data of virtual machines on ESX Server without having to install backup software on the virtual machines. VCB consists of a set of utilities and scripts that work in conjunction with third-party backup software to backup virtual machine data. VCB and the third-party backup software are typically installed on a backup proxy server that uses the Microsoft Windows Server 2003 operating system by Microsoft Corporation. VCB supports file-level backups (backups at the level of files and directories) for virtual machines using Microsoft Windows operating systems. In a file-level backup, the granularity of the backup is at the level of individual files and/or directories of the virtual machine. A file-level backup allows copies of individual files on virtual disks to be made. File-level backups can be full backups, differential backups, or incremental backups.
VCB also supports image-level backups for virtual machines using any operating system (e.g., Microsoft Windows operating systems, Linux operating systems, or other operating systems that may be installed upon ESX Server). In an image-level backup, the granularity of the backup is at the level of a virtual machine (i.e., the entire virtual machine, including its current state is backed up). For an image-level backup, typically the virtual machine is suspended and all virtual disk and configuration files associated with the virtual machine are backed up, and then the virtual machine is resumed.
An administrator would typically choose to perform a file-level backup of a Microsoft Windows virtual machine because of the potential need to restore individual files or directories from the backed-up Microsoft virtual machine. However, VCB may not perform a file-level backup of a Microsoft Windows virtual machine as quickly as an image-level backup. Accordingly, a system that enables a backup of a Microsoft Windows virtual machine to be performed at least as quickly as a file-level backup and enables granular restoration of any data (e.g., individual files or directories) from the backed-up Microsoft virtual machine would have significant utility.
Because VCB only supports file-level backups for virtual machines using Microsoft Windows operating systems, a file-level backup cannot be performed using VCB for virtual machines using operating systems other than Microsoft Windows (e.g., Linux operating systems). An administrator must back up a non-Microsoft Windows virtual machine using an image-level backup. Therefore, in order to granularly restore data (e.g., an individual file or directory) from the backed-up non-Microsoft Windows virtual machine, the entire non-Microsoft Windows virtual machine must be restored. This may require overwriting the original virtual machine with the backed-up virtual machine, or re-creating the original virtual machine on a different physical machine. This may be a laborious and time-intensive process, and may result in loss of virtual machine data. Accordingly, a system that enables the granular restoration of any data (e.g., individual files or directories) within a virtual machine using any type of operating system would have significant utility.
Another challenge posed by the use of VCB to perform backups of virtual machines is that such backups require an administrator to manually identify or specify the virtual machines that are to be backed up, typically via a script created in advance of the backup operation. However, because virtual machines may be easily set up and torn down, virtual machines may be less permanent in nature than actual physical machines. Due to this potential transience of virtual machines, it may be more difficult for the administrator to identify all of the virtual machines which are to be backed up in advance of the backup operation. Accordingly, a system that provides automatic identification of virtual machines that are to be backed up at the time of the backup operation would have significant utility.
The need exists for a system that overcomes the above problems, as well as one that provides additional benefits. Overall, the examples herein of some prior or related systems and their associated limitations are intended to be illustrative and not exclusive. Other limitations of existing or prior systems will become apparent to those of skill in the art upon reading the following Detailed Description.